While a variety of modifiers which can be compounded in thermoplastic resins as flame retardants, compatibilizing agents, antistatic agents or the like are known in the art, there is a continuous need for novel modifiers. For example, JP-A 8-302120 describes a thermoplastic resin having a sulfonate salt group as a polar group and specifically uses maleic anhydride-modified polyphenylene ether in Examples, but does not refer to its general structure and preparation method. JP-A 2003-213125 describes a polar group-modified polyphenylene ether which serves as a compatibilizing agent for polyamide resins and polystyrene resins, with sulfonate salt groups being exemplified as the polar group. In Examples, maleic anhydride-modified polyphenylene ether is used as in the previous JP-A 8-302120. Since the maleic anhydride-modified polyphenylene ether is prepared by radical modification, it is deemed to have such a structure that a polar group is introduced at the 2-methyl position on the terminal phenol forming the polyphenylene ether skeleton. A percent acid modification is calculated to be 2% or less. It is presumed to be a polymer having a weight average molecular weight of about 20,000 since the process starts with a polyphenylene ether having an intrinsic viscosity of 0.47 dl/g.
Meanwhile, polycarbonate resins are widely used in the industry including automobile, business machine, electric and electronic fields. In those applications such as business machines and electric and electronic equipment among others, it is strongly desired that the resin materials used be flame retardant. To meet such a demand, a number of flame retardants have been developed and investigated. In the prior art, for rendering polycarbonate resins flame retardant, bromine compounds are exclusively used. Sometimes antimony trioxide is used in combination. Resin compositions containing such compounds, however, suffer from the problem that they evolve bromine gas when burned, causing environmental pollution. Recently it was reported to use phosphorus based flame retardants (e.g., phosphoric esters) alone or in combination with bromine compounds for the purpose of reducing the amount of bromine compounds used. The phosphorus based flame retardants have the drawback that they decompose during service, detracting from the mechanical strength of the resin compositions. They do not fully overcome the problem of environmental pollution.
The non-phosphorus flame retardant materials or non-phosphorus, non-bromine flame retardant materials which are known in the art include a flame retardant polycarbonate resin composition comprising an alkali metal or alkaline earth metal salt of an organic acid such as sulfonic acid, polytetrafluoroethylene, and an aromatic polycarbonate (JP-A 51-45159); a flame retardant polycarbonate resin composition comprising a polycarbonate, an alkali metal or alkaline earth metal salt of perfluoroalkanesulfonic acid, and an epoxy resin (JP-A 6-73281); and a flame retardant polycarbonate resin composition comprising a polycarbonate resin, a metal salt of aromatic sulfur compound, a fluorinated polymer of fibrillation type, and an organopolysiloxane (JP-A 2004-155938). These flame retardant polycarbonate resin compositions, however, have several drawbacks. The transparency characteristic of polycarbonate resin is lost. Also, if the flame retardant is added in a sufficient amount to exert flame retardant effect, it can compromise the heat stability of the resin composition in the melt, resulting in molded parts suffering from yellowing, silver streaking and even a substantial reduction of mechanical strength.
JP-A 2003-64229 discloses a flame retardant polycarbonate resin composition comprising a polycarbonate resin and a sulfonic acid metal salt of a styrenic polymer in which aromatic monomer units having a sulfonic acid group incorporated in the aromatic skeleton account for 15 to 45 mol % of the entire monomer units and which contains up to 5% by weight of a metal sulfuric acid salt. This composition is thermally unstable, prone to yellowing and unsatisfactorily weather resistant.
The above-described resin compositions having halogen- or phosphorus-free flame retardants compounded therein have several drawbacks that they achieve only insufficient flame retardance, or if the flame retardant is added in a sufficient amount to exert flame retardant effect, it can compromise the heat stability of the resin composition in the melt, resulting in molded parts suffering from yellowing and even a substantial reduction of mechanical strength.
To further enhance or improve the properties of polycarbonate resins, a number of polymer alloys thereof with other thermoplastic resins have been developed. One typical polymer alloy is a composition comprising a polycarbonate resin and a styrene/acrylonitrile graft copolymer such as ABS resin which is used in automobile, electric and electronic and other fields as a thermoplastic resin material having excellent mechanical, rheological and thermal properties. Where flame retardance is required, a flame retardant is added to the composition. Halogen-free flame retardant materials which are known to impose a less burden to the environment include materials having phosphorus-based flame retardants compounded in resin compositions comprising a polycarbonate resin and an ABS resin (see JP-A 2-115262 and JP-A 2-32154). They still suffer from a drop of deflection temperature under load and mold deposits.
JP-A 11-172063 discloses a resin composition comprising a resin composition composed of a polycarbonate resin, an ABS resin and the like, and a sulfonic acid metal salt of polystyrene. If the sulfonic acid metal salt of polystyrene is added in a sufficient amount to exert flame retardant effect, the resulting resin composition has a lower impact strength and a lower deflection temperature under load, and the molded parts have an unsatisfactory outer appearance. JP-A 2002-167499 discloses a flame retardant resin composition comprising a polycarbonate resin, a styrene resin, and a polymer comprising silicon, boron and oxygen, having a skeleton consisting essentially of silicon-oxygen bonds and boron-oxygen bonds and having an aromatic ring in a molecule although it is insufficient in flame retardance and impact strength. JP-A 2004-35587 discloses a resin composition comprising a polycarbonate resin, a styrene resin, an organic alkali metal salt and/or organic alkaline earth metal salt, and a functional group-containing silicone compound although it has a low impact strength and weld strength.
As mentioned above, resin compositions comprising polycarbonate resins, styrene resins such as ABS resins and flame retardants are less practical in that their deflection temperature under load, impact strength, and weld strength are low, they leave mold deposits and provide a defective outer appearance.